Toyota Repair: Valve Train Noise, puff of smoke, train noise

Question
First, thanks for your time-I have read your Q&A for years.

'92 Corolla (4AFE), 156K, original owner; maintained as schedule dictates. Very minor issues over the years.

Car runs great. But, I have noticed a very slight, but detectable noise from the valve train. It almost sounds like soft diesel clatter. And it comes and goes. (No work has been done to the head-I remember other answers about failure to use service bolts during disassembly).

This car always had some valve clatter-never was a big deal. I know you have always stated a knocking sound is never good (understandably).

I know it is hard to speculate from a distance. I guess my question is more if I should really be terribly worried. I do get the valve stem puff of smoke very occasionally (you said the As weren't prone to this like my S)

Your thoughts?

Answer
It may just need to have the valves adjusted, they use shim type valve adjusters which is pretty involved and not really something you would want to do yourself because it involves using different size shims which are kind of expensive so this is best left to the dealer or a shop that knows Toyotas real well.